Carpet binding machines are used to sew binding material, or tape, to the top and bottom of a piece of carpet to bind the edge of the carpet. Oftentimes, in a wall-to-wall carpet installation, a four or six inch strip of contrasting carpet will be used as coving instead of wood or rubber cove molding. In such an installation, the upper edge of the carpet cove needs binding material sewn thereon to present a finished appearance and so that the edge does not unravel. The stitch utilized by most carpet binding machines is the federal stitch type 401 chain stitch because of its streamlined appearance and effective binding capability.
Carpet binding machines are generally classified as being portable or stationary. Stationary machines are heavy, often weighing between 55 and 65 pounds. The weight of such machines forces them to be used at a single location, for example, in a carpet installer's warehouse, to sew binding material onto a carpet edge. While such machines tend to be durable, their lack of portability limits their usefulness in situations where the carpeting cannot be precut into appropriate length pieces for the job and bound in the installer's warehouse. Also, such stationary machines tend to be costly compared to their portable counterparts.
Portable carpet binding machines have the advantage of being capable of being transported and used at installation sites by installers. They do not require the carpeting to be precut and prebound as with a stationary machine and are lower in cost than stationary machines. However, the durability and reliability of most prior art portable carpet binding machines has been unsatisfactory.
Portable carpet binding machines are manufactured by modifying a standard household sewing machine. While such sewing machines are suitable for sewing clothes and similar light fabrics, subjecting such machines to the rigors of sewing carpeting characterized by heavy backing material and a plush pile results in an undesirable rate of skipped or otherwise malformed stitches, carpet feed problems, or even sewing machine breakdowns.
A skipped or malformed stitch can be corrected at the installation site. However, because such problems recur with frequency, oftentimes taking the time to restitch a piece of carpet can result in substantial delays and inconvenience.
A skipped stitch may occur in a type 401 stitch sewing cycle, for example, if the needle loop is not properly formed and the looper misses the opening of the needle loop as a result. Because portable carpet binding machines typically use a plastic needle thread, there is a greater tendency for the needle thread to flex in an unpredictable manner and, therefore, create unpredictable sewing results. Oftentimes, a single skipped stitch will cause the succeeding stitch to be missed because the previously improperly formed needle loop generates additional slack in the needle thread making it difficult to form the next needle loop. A series of missed stitches can cause an unsightly gap in the stitching of the binding material and a risk of the carpet edge unraveling.
A malformed stitch may occur, for example, if there is too much slack in the needle thread or looper thread. A household sewing machine incorporates thread take-up mechanisms to remove slack in the threads. These thread take-up mechanisms, however, are not designed to be used in a portable carpet binding machine. Some prior art portable carpet binding machines that modify such household sewing machines fail to adequately modify the thread take-up mechanism, which, in turn, can cause such malformed stitches.
A malformed stitch can also occur when the piece of carpet is not fed properly through the sewing machine. Portable carpet binding machines that are made from a modified household sewing machine utilize what is known in the art as a presser foot and feed-dog to feed the carpet. It has been found that this single feed assembly is unsatisfactory for feeding a piece of carpet. Furthermore, the rigors of carpet binding may subject components of the machine to undue stress and cause excessive wear or failure in the components.
Since most carpet installers can only afford a single carpet binding machine, a breakdown of the machine requires the installer to quit working on the installation, take the machine to a repair shop, procure needed repairs and then return to the installation site to finish the job. The downtime of a portable carpet binding machine, whether due to restitching or repairing, results in downtime of the installer in addition to the expense of repair of the machine. Since most installers are paid by the job, downtime has a direct impact on the number of jobs completed by the installer and his or her net income.
Because of the thickness and stiffness of the carpet being bound, another problem with prior art carpet binding machines is their tendency to pull or angle away from the carpet edge while the machine moves along the carpet. This is typically caused by an insufficient carpet feeding assembly and results in poor appearance of the resulting bound carpet edge. When the binding machine angles away from the carpet edge as is moves along the carpet, the stitching and binding material are angled with respect to the edge of the carpet. Moreover, instead of the binding material being snugly pulled and stitched around the edge of the carpet, excess binding material gathers loosely around the carpet edge providing an unsightly appearance and poor durability.
One portable carpet binding machine that represented a significant advance in the art was the machine disclosed in U.S. Pat. No. 5,875,723 to Lobur. The '723 patent is incorporated herein in its entirety by reference. The '723 patent disclosed a portable carpet binding machine that included a novel carpet feeding assembly with a feed driver mechanism and coacting puller mechanism acting in synchronization to pull the carpet through the sewing mechanism.
While the carpet binding machine disclosed in the '723 patent proved to be a lightweight, yet rugged and durable machine, certain improvements were desirable to further improve the feed drive mechanism such that even the heaviest and thickest carpet would be pulled linearly through the sewing mechanism and the machine would not tend to pull away from the edge of the carpet.
What is needed is a portable carpet binding machine that is adapted to sewing light or heavy pile carpeting and that includes a carpet feeding assembly that feeds the carpet linearly through a sewing assembly and that moves the machine uniformly along an edge of the carpet. What is further desired is an upper direct drive mechanism within close proximity to the existing puller mechanism, wherein the upper direct drive mechanism is capable of vertical movement to compensate for varying thicknesses in the carpet material. It is desirable to accomplish such vertical movement of the upper drive mechanism through a direct connection with a minimal number of parts, such as universal joints, linkages, and bushings, which increase the cost of the machine and decrease efficiency. What is also needed is a portable carpet binding machine that is lightweight and that is more durable and reliable than prior art portable carpet binding machines. Such a machine must also be easy to manufacture and repair and be competitively priced with prior art portable carpet binding machines.